JP6806085B2 - Abrasive slurry regeneration method - Google Patents

Description

The present invention relates to a method for regenerating an abrasive slurry. In particular, the present invention relates to a method for regenerating an abrasive slurry capable of efficiently regenerating an abrasive slurry having a high polishing rate.

In recent years, the frequency of use of glass materials has increased for applications such as glass discs, quartz wafers and liquid crystal panels, and it is often essential that the surfaces of these glass materials be polished in a mirror shape. As the polishing method, CMP (Chemical Mechanical Polishing) technology for polishing the glass material with a polishing material slurry interposed between the polishing member such as a polishing pad and the glass material is generally adopted. ing.

When the content of the object to be polished such as fine glass pieces in the abrasive slurry increases due to polishing, the polishing rate of these abrasive slurries decreases. Therefore, these abrasive slurries are usually used for a certain period of time and then discarded. ing.

Among the main elements that make up the abrasive particles contained in the abrasive slurry, there are also rare metals obtained from minerals that are produced in small quantities or never produced in Japan. This material is a valuable resource that relies on imports in part, is often expensive in terms of material price, and is an important material that is also used in large amounts as abrasive particles. Therefore, it is strongly desired to effectively utilize the valuable material by recovering the abrasive slurry used in the polishing step and then regenerating it and using it as the recycled abrasive slurry.

Therefore, for example, in order to remove the component derived from the abrasive from the recovered abrasive slurry, a method of adding a dispersant or an electrolyte to dissolve the component derived from the object to be polished to regenerate the abrasive slurry is disclosed. (See, for example, Patent Documents 1 and 2).

Here, in the abrasive slurry, together with the abrasive particles (also referred to as abrasive grains) which are the main components, the purpose is to improve the dispersibility, cleanability, abrasiveness, etc. of the abrasive particles during polishing and increase the polishing speed. , Stabilizers, cleaning agents and the like (hereinafter, the additive having the ability to increase the polishing rate is also referred to as additive A) may be contained. In addition, when the abrasive slurry contains additives such as antibacterial agents, preservatives and antifreeze agents from the viewpoint of maintaining stability during storage and transportation from the time of manufacture to the actual use for polishing. (See, for example, Patent Documents 3 and 4), and some of the additives have a function of lowering the polishing rate (hereinafter, the additive having the ability to reduce the polishing rate is also referred to as additive B). .). Additive B is an unnecessary material from the viewpoint of maintaining and improving the polishing rate in the regenerated abrasive slurry which is often used immediately after regeneration.

However, according to the techniques described in Patent Documents 1 and 2, the additive A may be removed by the regeneration step, or the additive B may remain in the regenerated abrasive slurry. Therefore, in order to obtain a recycled abrasive slurry having a high polishing rate, it is necessary to add the additive A again or remove the additive B after the regeneration step, and the abrasive slurry having a high polishing rate is required. It was difficult to obtain efficiently.

Japanese Unexamined Patent Publication No. 6-254764 Japanese Unexamined Patent Publication No. 2003-205460 JP-A-2002-114967 Japanese Unexamined Patent Publication No. 2013-222863

The present invention has been made in view of the above problems and situations, and a solution thereof is to provide a method for regenerating an abrasive slurry capable of efficiently regenerating an abrasive slurry having a high polishing rate. ..

As a result of investigating the causes of the above problems in order to solve the above problems according to the present invention, an abrasive slurry containing abrasive particles and a plurality of types of additives is used, and an abrasive containing silicon oxide as a main component is used. The method for regenerating the recovered abrasive slurry after polishing the abrasive is to regenerate the recovered abrasive slurry, among the additives contained in the recovered abrasive slurry, an additive having a molecular weight of 500 or more and an abrasive particle. We have found that an abrasive slurry having a high polishing rate can be efficiently regenerated by having a regeneration step of recovering the additive adsorbed on the abrasive together with the abrasive particles, and have reached the present invention.
That is, the problem according to the present invention is solved by the following means.

1. 1. An abrasive slurry that regenerates the recovered abrasive slurry after polishing an object to be polished containing silicon oxide as a main component using an abrasive slurry containing abrasive particles and a plurality of types of additives. It ’s a playback method,
The relative abrasive concentration of unused abrasive slurry when used in polishing of the object to be polished (wt%), maintaining the abrasive concentration (mass%) in the range from 0.2 to 1 000% of However, among the additives contained in the recovered abrasive slurry, the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles are recovered together with the abrasive particles. A method for regenerating an abrasive slurry, which is characterized by the above.

2 . While maintaining the abrasive concentration (mass%) within the range of 1 to 1000% with respect to the abrasive concentration (mass%) of the unused abrasive slurry when used for polishing the object to be polished, the above. The method for regenerating an abrasive slurry according to item 1, wherein a regenerating step is performed.

According to the present invention, it is possible to provide a method for regenerating an abrasive slurry capable of efficiently regenerating an abrasive slurry having a high polishing rate.
Although the mechanism of expression or mechanism of action of the effect of the present invention has not been clarified, it is inferred as follows.
Whether or not the additive is adsorbed on the abrasive particles depends on the ratio of hydrophobic and hydrophilic groups of the additive, van der Waals force, pH of the abrasive slurry, abrasive concentration, and the concentration of the object to be polished. Dependent.
Further, among the additives contained in the recovered abrasive slurry, many of the additives having a function of lowering the polishing rate have a molecular weight of less than 500 or are difficult to be adsorbed on the abrasive particles due to the above conditions, and the polishing rate. Most of the additives having a function of improving the above conditions have a molecular weight of 500 or more or are easily adsorbed on the abrasive particles under the above conditions.
In the present invention, the abrasive concentration (mass%) is set to 0.2 with respect to the abrasive concentration (mass%) of the unused abrasive slurry when it is used for polishing the object to be polished during the regeneration process. By keeping the content within the range of ~ 3000%, it is possible to easily recover the additives contained in the recovered abrasive slurry and having a molecular weight of 500 or more and the additives adsorbed on the abrasive particles. Can be done.
This is because by setting the abrasive concentration to 0.2% or more, it is possible to prevent the amount of the solvent (mainly water) in the abrasive slurry from increasing too much, and to keep the pH of the abrasive slurry within a predetermined range. It can be inside, and the desorption of the additive adsorbed on the abrasive particles can be suppressed. Further, by suppressing the increase in the amount of the solvent, it is possible to prevent the additive from being hydrolyzed and the balance between the hydrophilic group and the hydrophobic group of the additive being disturbed, and the additive is desorbed adsorbed on the abrasive particles. Can be suppressed.
On the other hand, by setting the abrasive concentration to 3000% or less, the viscosity of the abrasive slurry can be kept low, the amount of adhesion loss to the inside of the container or device in which the regeneration step is performed is reduced, and the recovery rate is reduced. Can be improved.
Therefore, among the additives contained in the recovered abrasive slurry, the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles are added while maintaining the abrasive concentration during the regeneration step within the above range. By recovering the agent together with the abrasive particles, the abrasive slurry mainly containing the abrasive particles and the additive A can be efficiently obtained with a high recovery rate. Further, since the obtained abrasive slurry mainly contains the abrasive particles and the additive A, the abrasive slurry having a high polishing rate can be obtained according to the above method.

Schematic configuration of the polishing machine according to this embodiment Schematic diagram showing an example of a process for obtaining a recycled abrasive slurry from a recovered abrasive slurry. Schematic configuration diagram of the filter filtration device according to this embodiment Schematic diagram showing the constituent materials of the abrasive slurry at each stage from the unused abrasive slurry to the regenerated abrasive slurry.

In the method for regenerating the abrasive slurry of the present invention, the abrasive slurry containing the abrasive particles and a plurality of types of additives was used to polish the object to be polished containing silicon oxide as a main component, and then recovered. A method for regenerating an abrasive slurry that regenerates a recovered abrasive slurry, wherein the abrasive concentration (mass%) is relative to the abrasive concentration (mass%) of the unused abrasive slurry when used for polishing the object to be polished. while maintaining mass%) in the range of from 0.2 to 1 000%, it said of additives contained in recovered abrasive slurry, and a molecular weight of 500 or more additives, adsorbed to the abrasive particles It is characterized by having a regeneration step of recovering the added additive together with the abrasive particles. This feature is a technical feature common to or corresponding to each claim .
Also, in the reproducing method of the abrasive slurry of the present invention, the relative abrasive concentration of unused abrasive slurry when used in polishing of the object to be polished (mass%), the abrasive concentration (wt% ) Is preferably maintained within the range of 1 to 1000%, and the regeneration step is preferably performed. As a result, the number of defects when polishing with the obtained regenerated abrasive slurry can be reduced, and the abrasive recovery rate can be improved.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In addition, "~" shown in this invention is used in the meaning which includes the numerical values described before and after it as the lower limit value and the upper limit value.

<< Overview of how to regenerate abrasive slurry >>
In the method for regenerating the abrasive slurry of the present invention, the abrasive slurry containing the abrasive particles and a plurality of types of additives was used to polish the object to be polished containing silicon oxide as a main component, and then recovered. This is a method for regenerating an abrasive slurry that regenerates the recovered abrasive slurry, and the abrasive concentration (mass) is relative to the abrasive concentration (mass%) of the unused abrasive slurry when it is used for polishing the object to be polished. %) Is maintained in the range of 0.2 to 3000%, and among the additives contained in the recovered abrasive slurry, the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles Has a regeneration step of recovering the abrasive particles together with the abrasive particles.

Here, the object to be polished containing silicon oxide as a main component means an object to be polished containing 50% by mass or more of silicon oxide.
Further, in the regeneration step according to the present invention, the additive adsorbed on the abrasive particles shall be recovered together with the abrasive particles regardless of the molecular weight.

<< Preparation flow of recycled abrasive slurry >>
[Polishing process]
First, a polishing process for polishing an object to be polished will be described with reference to FIG. After the polishing step, a recovered abrasive slurry containing abrasive particles and the like is obtained.
FIG. 1 is a schematic configuration diagram of a polishing machine according to the present embodiment.

Taking the polishing of a glass lens as an example, the polishing process generally comprises a plurality of processes such as preparation of an abrasive slurry, polishing process, and cleaning of a polished portion.

The polishing machine 1 shown in FIG. 1 has a polishing surface plate 2 to which a polishing cloth F composed of a non-woven fabric, a synthetic resin foam, a synthetic leather, or the like is attached, and the polishing surface plate 2 is configured to be rotatable. ing.

At the time of polishing work, the polishing platen 2 and the holder H are pressed against the polishing surface plate 2 with a predetermined pressing force N by using a rotatable holder H to press the object 3 containing silicon oxide as a main component. To rotate. At the same time, the abrasive slurry 4 prepared in advance is supplied from the slurry nozzle 5 via the pump D1. The abrasive slurry 4 (used abrasive slurry) after being used in the polishing step is stored in the slurry tank T ₁ through the flow path 6, and is repeatedly circulated between the polishing machine 1 and the slurry tank T ₁ .

If necessary, the washing water 7 stored in the cleaning water storage tank T _2, to clean the polishing machine 1 and the object to be polished 3 by spraying the polishing portion from the washing water ejecting nozzle 8. Cleaning solution 10 containing abrasive particles after washing (the spent abrasive slurry) is through the pump D2, it is stored in the cleaning liquid storage tank T ₃ through the channel 9.

The cleaning liquid storage tank T ₃ is a tank for storing the cleaning liquid 10 after being used for cleaning (rinsing). The inside of the cleaning liquid storage tank T ₃ is constantly stirred by a stirring blade (not shown) in order to prevent precipitation and aggregation of abrasive particles and the like.

Further, the abrasive slurry 4 generated by polishing and stored in the slurry tank T ₁ and the cleaning liquid 10 containing the abrasive particles stored in the cleaning liquid storage tank T ₃ are scraped off from the object to be polished 3 together with the abrasive particles. It is in a state of containing glass components (abrasive particles) derived from the material to be polished, fragments of the polishing cloth F, and the like.
Hereinafter, specific treatments in the polishing process will be described.

(1) Preparation of Abrasive Slurry Additive A, which has the ability to add and disperse abrasive particles in a concentration range of 0.5 to 40% by mass with respect to a solvent such as water, and further increase the polishing rate. And additive B having the ability to reduce the polishing rate is added to prepare an unused abrasive slurry. This abrasive slurry is circulated and supplied to the polishing machine 1 as shown in FIG. 1 for use. As the abrasive particles, particles having an average particle diameter of several tens of nm to several μm are used.

(2) Polishing process As shown in FIG. 1, the polishing pad (polishing pad F) and the object to be polished 3 are brought into contact with each other, and the polishing pad F And the object to be polished 3 are moved relative to each other.

(3) Cleaning of Polished Part A large amount of abrasive particles are attached to the object to be polished 3 and the polishing machine 1 immediately after being polished. Therefore, after polishing, for example, pure water is supplied as cleaning water 7 instead of the abrasive slurry to clean the abrasive particles 3 and the abrasive particles adhering to the polishing machine 1. At this time, the cleaning liquid 10 containing the abrasive particles is discharged into the flow path 9.

In this cleaning operation, a certain amount of abrasive particles are discharged into the flow path 9, so that the amount of abrasive particles in the system is reduced. To compensate for this decrease, adding a new abrasive slurry against the slurry tank T _1. As the timing of addition, addition may be performed every one machining, or may be added every fixed number of machining.

[Abrasive slurry recovery process]
The abrasive slurry recovery step is a step of recovering the used abrasive slurry.

There are mainly the following two types of used abrasive slurries. One is abrasive slurry with the washing water used in the cleaning operation is stored in the cleaning liquid storage tank T ₃ (rinse slurry). Another is discarded after being given the number of manipulations using a abrasive slurry reserved in the slurry tank T ₁ (Life end slurry).

Therefore, in the abrasive slurry recovery step, one or both of the rinse slurry and the life-end slurry are recovered.

The recovered abrasive slurry (recovered abrasive slurry) contains abrasive particles in a range of approximately 0.1 to 20% by mass.

[Regeneration process]
In the regeneration step, the recovered abrasive slurry recovered after polishing the object to be polished is subjected to various treatments to regenerate the recovered abrasive slurry into a polishing material slurry (recycled abrasive slurry) in a state where it can be used for polishing. It is a process.
In the regeneration step, at least, among the additives contained in the recovered abrasive slurry, the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles are recovered together with the abrasive particles. It suffices if the removal process is included. Further, the regeneration step preferably includes a foreign matter removing treatment, a polishing object dissolution treatment, a continuous filtration treatment, an abrasive material concentration adjusting treatment, and the like, if necessary. In the present invention, the abrasive material concentration means the concentration (mass%) of the abrasive material particles in the abrasive material slurry.

In the regeneration step according to the present invention, the abrasive material concentration (mass%) is 0.2 to 3000 with respect to the abrasive material concentration (mass%) of the unused abrasive material slurry when used for polishing the object to be polished. Perform various treatments while maintaining within the% range. By maintaining the abrasive concentration at 0.2% or more, it is possible to prevent the amount of solvent in the recovered abrasive slurry from increasing too much, and the pH of the recovered abrasive slurry can be kept within a predetermined range, and the additive A can be maintained. Hydrolysis and the like can be suppressed. Therefore, the detachment of the additive A adsorbed on the abrasive particles can be suppressed, and the additive A can be efficiently recovered. By maintaining the abrasive material concentration at 3000% or less, the viscosity of the recovered abrasive material slurry can be kept low, and the amount of adhesion loss to the inside of the container or device in which the regeneration process is performed can be reduced.
Further, the abrasive concentration is preferably maintained in the range of 1 to 3000%, preferably in the range of 0.2 to 1000%, and is maintained in the range of 1 to 1000%. Especially preferable.

Here, in the present invention, the abrasive concentration of the unused abrasive slurry when used for polishing the object to be polished is the concentration required when the unused abrasive slurry is used for the first time in the polishing process. It is the abrasive concentration after adjustment, and refers to the abrasive concentration at the timing immediately before the start of the polishing process. For example, in the example shown in FIG. 1, the abrasive concentration at the timing immediately before the abrasive slurry stored in the slurry tank T ₁ starts to be supplied from the slurry nozzle 5 onto the abrasive surface plate 2 is set in the abrasive slurry. It shall do not include those flows into the slurry tank T ₁ through the channel 6.

The regeneration process according to the present invention will be described in detail with reference to FIGS. 2 and 3.
FIG. 2 is a schematic view showing an example of a process for obtaining a recycled abrasive slurry from a recovered abrasive slurry. FIG. 3 is a schematic configuration diagram showing a filter filtration device 20 used in the regeneration step according to the present invention.

(1. Foreign matter removal processing)
The recovered abrasive slurry obtained in the abrasive slurry recovery step includes the abrasive slurry used in the polishing step, cleaning water, and fragments of the polishing cloth and polishing pad.
In the foreign matter removing step, a filter having a pore size of 20 to 100 μm is used to remove foreign matter such as polishing cloth and debris of the polishing pad.

(2. Dissolution treatment of the object to be polished)
Next, the object to be polished is melted. The object to be dissolved treatment is a process for dissolving the object to be polished contained in the abrasive slurry in a solvent such as water. In the polishing material dissolution treatment, as described above, the abrasive material concentration (mass%) is 0. The abrasive material concentration (mass%) of the unused abrasive material slurry when used for polishing the abrasive material. It is carried out so as to be maintained within the range of 2 to 3000%.

Specifically, for example, as shown in FIG. 3, the recovered abrasive slurry 22 from which the foreign matter has been removed by the foreign matter removing treatment is put into the tank 21 of the filter filtration device 20 provided with the temperature control unit.

Next, a solvent is added to the recovered abrasive slurry 22 in the tank 21 and stirred by a stirrer 25 equipped with a motor M to dissolve the object to be polished. As the solvent to be added, the main component is water.

The recovered abrasive slurry is preferably heated in the tank 21, and particularly preferably in the range of 40 to 90 ° C.

As described above, by adding a solvent and heating in some cases, the components of the object to be polished are dissolved, while the abrasive particles are not dissolved in the solvent. Therefore, the filter is used in the additive removal treatment described later. Can be separated.

In the polishing object dissolution treatment, after the polishing object is dissolved, the recovered abrasive slurry may be filtered separately from the additive removal treatment described later. As a result, the filtrate containing the object to be polished and a part of the solvent may be separated from the recovered abrasive slurry to remove the object to be polished from the recovered abrasive slurry.

(3. Additive removal treatment)
Next, in order to remove additives unnecessary for polishing, an additive removing treatment is performed in which the recovered abrasive slurry in which the components to be polished are dissolved by the object to be dissolved treatment is filtered using the filtration filter 26. In the additive removal treatment, as described above, the abrasive concentration (mass%) is 0.2 with respect to the abrasive concentration (mass%) of the unused abrasive slurry when used for polishing the object to be polished. It is carried out so as to be maintained within the range of ~ 3000%.

Specifically, among the additives contained in the recovered abrasive slurry, the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles are filtered under the condition that they can be recovered together with the abrasive particles. Do. Thereby, the filtrate containing the additive having a molecular weight of less than 500, a part of the solvent, and the component to be polished dissolved in the part of the solvent can be separated from the recovered abrasive slurry. The filtrate separated from the recovered abrasive slurry is discharged to the outside of the system when the on-off valve 27 is opened.

Since the additive B mainly has a molecular weight of less than 500 and is difficult to be adsorbed on the abrasive particles, most of the additive B is removed from the recovered abrasive slurry by the additive removing treatment.
On the other hand, since the additive A has a molecular weight of 500 or more or is often adsorbed on the abrasive particles, it is hardly removed by the additive removing treatment. Further, among the additives A, those having an original molecular weight of 500 or more and having a molecular weight of less than 500 due to decomposition or the like are removed from the recovered abrasive slurry by the additive removal treatment, but when they are decomposed or the like. Is preferably removed from the recovered abrasive slurry because the ability to increase the polishing rate is reduced.

The filter 26 is not particularly limited, and for example, a hollow fiber filter, a metal filter, a thread winding filter, a ceramic filter, a roll type polypropylene filter, or the like can be used.
As the ceramic filter, for example, a ceramic filter manufactured by TAMI of France, a ceramic filter of Noritake, a ceramic filter of NGK (for example, Cerarec DPF, Sepilt, etc.) and the like are preferably used.

It is also preferable to perform the additive removal treatment before performing the polishing object dissolution treatment, separate the filtrate containing an additive having a molecular weight of less than 500 and a part of the solvent, and then perform the polishing object dissolution treatment. .. The object to be polished can be efficiently removed by filtering the recovered abrasive slurry after the process of dissolving the object to be polished.
Further, the additive removal treatment is not limited to filtration as long as the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles can be recovered together with the abrasive particles, and is not limited to filtration, but is centrifugal separation or the like. Is also good.

(4. Continuous filtration treatment)
Next, the same amount of water as the filtrate separated from the recovered abrasive slurry in the additive removal treatment is added, and the operation of filtering again is repeated to perform a continuous filtration treatment for removing unnecessary additives and the object to be polished. Do. Further, as described above, in the continuous filtration treatment, the abrasive material concentration (mass%) is 0, relative to the abrasive material concentration (mass%) of the unused abrasive material slurry when used for polishing the object to be polished. It is carried out so as to be maintained within the range of 2 to 3000%.

Specifically, while circulating the recovered abrasive slurry via the circulation pipe 23, the above-mentioned dissolution treatment of the object to be polished and the additive removal treatment are continuously performed over a predetermined time. When the concentration of the additive B in the recovered abrasive slurry has decreased to a predetermined concentration, the three-way valve 24 is switched to the discharge side, and the additive-removed abrasive slurry is discharged to the outside of the system and recovered. The time and number of times and the number of times of the object dissolution treatment and the additive removal treatment in the continuous filtration treatment may be appropriately set according to the configuration of the filter filtration device 20, the components of the recovered abrasive slurry, and the like.

The concentration of Additive B in the abrasive slurry with the additive removed is within the range of 0.2 to 50% of the concentration of the unused abrasive slurry when used for polishing the object to be polished. It is preferable to reduce the concentration.

In the present invention, the content of each additive in the abrasive slurry can be quantified using, for example, high performance liquid chromatography (HPLC).

(5. Abrasive concentration adjustment process)
Next, an abrasive concentration adjusting treatment for adjusting the abrasive concentration is performed on the additive-removed abrasive slurry obtained through the continuous filtration treatment. Further, in the abrasive concentration adjusting treatment, as described above, the abrasive concentration (mass%) is higher than the abrasive concentration (mass%) of the unused abrasive slurry when used for polishing the object to be polished. It is carried out so as to be maintained within the range of 0.2 to 3000%.

Specifically, the concentration of the abrasive is adjusted by concentrating it by filtration or the like, or diluting it by adding water or the like.
The regeneration step is performed as described above.

[Additive replenishment process]
Next, the additive replenishment step of setting the replenishment amount of the additive A to be replenished with respect to the additive-removed abrasive slurry obtained in the regeneration step and replenishing the set replenishment amount of the additive is performed. Is also good. According to the method for regenerating the abrasive slurry of the present invention, the additives required for the abrasive slurry can be recovered together with the abrasive particles, so that the additive replenishment step may be performed as needed.

Specifically, the electrical conductivity of the additive-removed abrasive slurry is measured, the replenishment amount to be added is set according to the measured value, and the additive of the set replenishment amount is used as the additive-removed abrasive. Add to the slurry. As the replenishment amount of the additive A, the value of the electric conductivity of the abrasive slurry finally obtained after being regenerated is the value of the electric conductivity of the unused abrasive slurry when used for polishing the object to be polished. It is preferable to set the value so as to be in the range of 0.05 to 100 times.

For the measurement of electrical conductivity, for example, an electric conductivity meter (ES-51 manufactured by HORIBA, Ltd.), an electric conductivity meter (CM-30G manufactured by Toa DKK Co., Ltd.), a Lacom tester handy type conductivity meter CyberScan CON110 (AS ONE Co., Ltd.), a compact electric conductivity meter LAQUAtwin B-771 (manufactured by HORIBA, Ltd.), or the like, the sample liquid can be measured and measured at a temperature of 25 ° C.

The amount of additive A replenished at this time should be within a concentration range of 0.1 to 50 times the concentration of additive A in the unused abrasive slurry when used for polishing the object to be polished. It is preferable to set to.

For example, in an unused abrasive slurry used for polishing an object to be polished, when the abrasive concentration is 1.0% by mass and the concentration of additive A is 0.02% by mass, the regenerated abrasive slurry is used. When the abrasive concentration is 1.0% by mass, the replenishment amount of the additive A is preferably set so that the concentration of the additive A is in the range of 0.002 to 1.0% by mass.

<< Regeneration flow of abrasive slurry and balance of constituent materials in each process >>
FIG. 4 is a schematic view showing the constituent materials of the abrasive slurry at each stage from the unused abrasive slurry described above to the regenerated abrasive slurry.

First, when used for polishing an object to be polished, the unused abrasive slurry 31 contains the liquid medium Dm (mainly water), the abrasive particles (abrasive grains) PM which are the main materials, and the polishing rate. additives a ₁ with elevated ability _and an additive B having a reducing ability of the polishing rate are contained. As the additive B, an antiseptic, an antibacterial agent, or the like for ensuring storage stability and the like during the period from the preparation of the abrasive slurry to the use in the polishing step is used.

After performing a polishing step using the unused abrasive slurry 31, a polishing material slurry recovery step is performed to recover the recovered abrasive slurry 32. The recovered abrasive slurry 32 contains, in addition to the constituent materials of the unused abrasive slurry 31, the polished residue S and the like generated in the polishing step.

A regeneration step is performed on the recovered abrasive slurry 32. In the example shown in FIG. 4, the regeneration step includes a process for dissolving the object to be polished and a treatment for removing additives, but further includes one or more of the above-mentioned foreign matter removing treatment, continuous filtration treatment, and abrasive concentration adjusting treatment. It may be a thing. In the regeneration step, the abrasive material concentration (mass%) is 0.2 to 3000% of the abrasive material concentration (mass%) of the unused abrasive material slurry when used for polishing the object to be polished. It is preferable to perform various treatments so as to be maintained within the range.

Next, the object to be polished is dissolved to dissolve the object to be polished S, and the filter filtration device 20 shown in FIG. 3 is used to remove additives from the recovered abrasive slurry 33 in which the object to be polished S is dissolved. Perform processing. As described above, the additive removal treatment is performed under the condition that the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles can be recovered together with the abrasive particles. Thus, from the recovery abrasive slurry 33, the filtrate 34 containing additive B are separated, and the additive A ₁ is recovered with the abrasive particles PM, additives-removed abrasive slurry 35 as a reproduced abrasive slurry can get. At this time, the additive A ₁ may be recovered in a state of being adsorbed on the abrasive particles PM, or may be recovered alone. Although not shown, the component molecular weight is less than 500 by decomposition of the additive A ₁ is included with the additive B to the filtrate 34.
Although not shown, the filtrate 34 may contain a small amount of the additive A _{1, and the} abrasive slurry 35 from which the additive has been removed may contain a small amount of the additive B.

In the abrasive slurry 35 from which the additive has been removed, the polishing rate is high because the content of the additive B is reduced, and the replenishment step of the additive A is not essential because the additive A remains. Therefore, according to the method for regenerating the abrasive slurry of the present invention, it is possible to efficiently regenerate the abrasive slurry having a high polishing rate.

Although it is not essential, as shown in FIG. 4, the additive-replenished abrasive slurry 35 may be subjected to an additive replenishment step, and the obtained additive-replenished abrasive slurry 36 may be used as a recycled abrasive. It may be a slurry. In the additive replenishment step, the concentration of the additive A ₁ (including the additives A ₁ and A ₂ ) is relative to the concentration of the additive A ₁ of the unused abrasive slurry 31 when used for polishing the object to be polished. It is preferable to supplement the additive A ₂ so that the concentration is in the range of 10 to 5000%. The additive A ₂ may be the same as or different from the additive A ₁ .

<< Abrasive slurry constituent materials >>
Next, details of the main constituent materials of the abrasive slurry according to the present invention will be described.

[Abrasive particles]
Generally, as an abrasive slurry used for polishing optical glass, semiconductor substrates, etc., for example, fine particles such as red iron oxide (αFe ₂ O ₃ ), cerium oxide, aluminum oxide, manganese oxide, zirconium oxide, and colloidal silica are added to water or oil. It is used that is dispersed in a slurry.

The method for regenerating an abrasive slurry of the present invention has a physical action and a chemical action in order to obtain a sufficient processing speed while maintaining flatness with high accuracy in polishing the surface of a semiconductor substrate or glass. It is preferable to apply it to an abrasive slurry that can be applied to chemical mechanical polishing (CMP), which is polished by both. The abrasive particles contained in the abrasive slurry are preferably selected from, for example, cerium oxide, diamond, boron nitride, silicon carbide, alumina, alumina zirconia and zirconium oxide.

Examples of the abrasive particles according to the present invention include synthetic diamond and natural diamond as the diamond-based abrasive. Examples of the boron nitride-based abrasive are abrasives having hardness next to diamond, and examples thereof include cubic boron nitride BN (for example, manufactured by Showa Denko KK). Examples of the silicon carbide-based abrasive include silicon carbide, green silicon carbide, and black silicon carbide. Examples of the alumina-based abrasive include brown alumina, white alumina, pink alumina, crushed alumina, alumina zirconia-based abrasive, and the like, in addition to alumina. Examples of zirconium oxide include BR series zirconium oxide for abrasives manufactured by Daiichi Rare Element Chemical Industry Co., Ltd.

The abrasive particles used in the present invention are not particularly limited in terms of their components and shapes, and generally commercially available abrasive particles can be used.

As a method for dispersing the abrasive particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to the dispersion treatment with a normal stirrer. The average particle size of the abrasive particles in the abrasive slurry thus produced is preferably in the range of 0.01 to 1.0 μm. If the average particle size of the abrasive particles is 0.01 μm or more, a high polishing rate can be obtained, and if it is 1.0 μm or less, scratches on the surface of the object to be polished should be prevented. Can be done.

[Additive]
The additive contained in the abrasive slurry according to the present invention is roughly classified into an additive A having an ability to increase the polishing rate and an additive B having an ability to decrease the polishing rate.

The "additive having the ability to increase the polishing rate" and the "additive having the ability to decrease the polishing rate" in the present invention are defined as compounds satisfying the conditions specified below.

First, the polishing rate 1 is measured according to the following method using the standard abrasive slurry 1 in which only the abrasive particles are dispersed in water at a concentration of 1.0% by mass.

Using the polishing machine shown in FIG. 1, the surface to be polished is polished with a polishing cloth while supplying the polishing material slurry 1 to the surface to be polished. In the polishing test, the polishing material slurry 1 was circulated and supplied at a flow rate of 5 L / min for polishing. A glass substrate having a thickness of 65 mm was used as the object to be polished, and a polyurethane cloth was used as the polishing cloth. The polishing pressure on the polished surface was 9.8 kPa (100 g / cm ² ), the rotation speed of the polishing tester was set to 100 min ^-1 (rpm), and the polishing process was performed for 30 minutes. The thickness before and after polishing was measured with a Nikon Digimicro (MF501), and the polishing amount (μm) per minute was calculated from the thickness displacement, and this was defined as the polishing rate 1.

Next, an abrasive slurry 2 to be measured containing the additive A or the additive B to be measured at a concentration of 0.02% by mass and the abrasive particles at a concentration of 1.0% by mass was prepared, and the same method as described above was used. The polishing speed 2 is measured.

Next, the polishing rate ratio (polishing rate 2 / polishing rate 1) was obtained from each of the obtained polishing rates, and if the polishing rate ratio was less than 1.00, the additive was an additive having the ability to reduce the polishing rate. If the polishing rate ratio is 1.02 or more, it is defined as an additive having the ability to increase the polishing rate. The additive having the ability to increase the polishing rate preferably has a polishing rate ratio of 1.05 or more, and more preferably 1.10 or more.

[Additive A: Additive having the ability to increase the polishing rate]
Additive A applicable to the present invention is an additive having a function of increasing polishing efficiency, and is mainly used.
(1) Dispersant that improves the dispersion stability of abrasive particles,
(2) _Si 3 _{N 4} film _SiO 2 / _Si 3 _{N 4} film selective ratio improver for improving the polishing rate of the SiO ₂ film to the polishing rate of
(3) A cleaning agent having an effect of improving detergency,
And so on.

Hereinafter, representative compounds of Additive A applicable to the present invention are listed, but the compounds are not limited to those exemplified here.

(Dispersant)
Examples of the dispersant include a water-soluble anionic dispersant, a water-soluble cationic dispersant, a water-soluble nonionic (nonionic) dispersant, a water-soluble amphoteric (betaine) dispersant, and the like. A dispersant which is a polymer compound containing an ammonium acrylate salt as a polymerization component is preferable. For example, ammonium polyacrylate, a copolymer of acrylic acid amide and ammonium acrylate, and the like can be mentioned.

In addition, two or more of the above dispersants may be used in combination in the abrasive slurry according to the present invention. For example, at least one type of polymer dispersant containing an ammonium acrylate as a copolymerization component, a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, and a water-soluble amphoteric dispersant. At least one selected from the agents may be used in combination.

When the abrasive slurry is used for polishing related to the production of a semiconductor element, the content of an alkali metal such as sodium ion or potassium ion in the dispersant is preferably suppressed to 10 ppm or less.

The amount of the dispersant added depends on the dispersibility and sedimentation prevention of the abrasive particles in the abrasive slurry, and the relationship between the polishing scratches and the amount of the dispersant added. For example, when the abrasive particles are cerium oxide, the cerium oxide particles are added. It is preferably in the range of 0.01 to 2.0 parts by mass with respect to 100 parts by mass. The molecular weight of the dispersant is preferably in the range of 500 to 50,000, more preferably 1000 to 10000. When the molecular weight of the dispersant is 500 or more, a sufficient polishing rate can be obtained when polishing the silicon oxide film or the silicon nitride film as the object to be polished, and when the molecular weight of the dispersant is 50,000 or less, polishing is performed. It is possible to suppress an increase in the viscosity of the material slurry and ensure storage stability. When the dispersant is a polymer having a molecular weight of 10,000 or more, the preferable molecular weight of the dispersant is a weight average molecular weight.

<Anionic dispersant>
Examples of the anionic dispersant include triethanolamine lauryl sulfate, ammonium lauryl sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, and polycarboxylic acid type polymer dispersants.

Examples of the polycarboxylic acid type polymer dispersant include a polymer of a carboxylic acid monomer having an unsaturated double bond such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid, and an unsaturated double bond. Examples thereof include a copolymer of a carboxylic acid monomer having a carboxylic acid monomer and another monomer having an unsaturated double bond, and an ammonium salt and an amine salt thereof.

<Cationic dispersant>
Examples of the cationic dispersant include primary to tertiary aliphatic amines, tetraalkylammonium, trialkylbenzylammonium alkylpyridinium, 2-alkyl-1-alkyl-1-hydroxyethylimidazolinium, N, N. -Dialkylmorpholinium, polyethylene polyamine fatty acid amide, urea condensate of polyethylene polyamine fatty acid amide, quaternary ammonium of urea condensate of polyethylene polyamine fatty acid amide, and salts thereof.

<Nonionic dispersant>
Examples of the nonionic dispersant include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octylphenyl ether, and polyoxyethylene. Nonylphenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene Solbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbit tetraoleate, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, Examples thereof include polyoxyethylene hydrogenated castor oil, 2-hydroxyethyl methacrylate, and alkyl alkanolamide.

<Betaine dispersant>
Examples of the betaine dispersant include N, N-dimethyl-N-alkyl-N-carboxymethylammonium betaine, N, N, N-trialkyl-N-sulfoalkyleneammonium betaine, N, N-dialkyl-N, Betaines such as N-bispolyoxyethylene ammonium sulfate betaine, 2-alkyl-1-carboxymethyl-1-hydroxyethyl imidazolinium betaine; aminocarboxylic acids such as N, N-dialkylaminoalkylene carboxylate Can be mentioned.

(Polishing speed selectivity improver)
In the abrasive slurry according to the present invention, when the object to be polished contains silicon nitride, a polishing rate selectivity improver can be applied as the additive A.
Improving the polishing rate selectivity in the present invention means improving the polishing rate ratio (hereinafter, also referred to as selection ratio) of the silicon nitride film (Si ₃ N ₄ ) to the polishing rate of the silicon oxide film (SiO ₂ ). To do.

In the present invention, as the polishing rate selectivity improver, an organic cationic compound is preferable from the viewpoint of being able to improve the ratio of the polishing rate of the silicon nitride film to the polishing rate of the silicon oxide film.

As the organic cation compound, a compound containing a nitrogen atom is preferable, and a compound having an amino group or a quaternary ammonium group is preferable. From the viewpoint of water solubility, the molecular weight of the organic cation compound is preferably in the range of 500 to 50,000, more preferably in the range of 1000 to 10000.

The compound having an amino group may contain one or more amino groups in one molecule, and the number thereof is preferably 1 to 20, more preferably 1 to 10, and further preferably 1 to 1 from the viewpoint of water solubility. 5, most preferably 1-3. The ratio (C / N ratio) of the number of carbon atoms and the number of nitrogen atoms contained in one molecule of the compound having an amino group is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 20 from the viewpoint of water solubility. 1 to 6, most preferably 1 to 4. However, ethanolamine compounds are excluded.

Specific compounds of each polishing rate selectivity improver include, for example, JP-A-2002-114967, JP-A-2002-118882, JP-A-2002-201462, JP-A-2004-269757, and special publications. Monoamines such as primary amines, secondary amines or tertiary amines, polyvalent amines, amines having an OH group, amines having an ether group, and nitrogen atoms described in Kai 2004-273547, etc. Examples thereof include heterocyclic compounds contained and compounds having a quaternary ammonium group.

Of these, ethylamine, propylamine, isopropylamine, butylamine and ethylenediamine are particularly preferred.

(Washing soap)
In the present invention, it is preferable to use a cleaning agent as one of the additives A, and it is particularly preferable to use an alcohol-based compound as a cleaning agent.

Examples of alcohol-based compounds that are cleaning agents applicable to the present invention include 1-propanol, 2-propanol, 2-propin-1-ol, allyl alcohol, ethylenecyanohydrin, 1-butanol, 2-butanol, (S). )-(+)-2-Butanol, 2-methyl-1-propanol, t-butyl alcohol, perfluoro-t-butyl alcohol, crotyl alcohol, 1-pentanol, 2,2-dimethyl-1-propanol, 2-Methyl-2-butanol, 3-methyl-1-butanol, S-amyl alcohol, 1-hexanol, 4-hydroxy-4-methyl-2-pentanone, 4-methyl-2-pentanol, cyclohexanol, DL -3-Hexyl alcohol, 1-heptanol, 2-ethylhexyl alcohol, (S)-(+) -2-octanol, 1-octanol, DL-3-octyl alcohol, 2-hydroxybenzyl alcohol, 2-nitrobenzyl alcohol, 3,5-Dihydroxybenzyl alcohol, 3,5-dinitrobenzyl alcohol, 3-fluorobenzyl alcohol, 3-hydroxybenzyl alcohol, 4-fluorobenzyl alcohol, 4-hydroxybenzyl alcohol, benzyl alcohol, m- (trifluoromethyl) Benzyl alcohol, m-aminobenzyl alcohol, m-nitrobenzyl alcohol, o-aminobenzyl alcohol, o-hydroxybenzyl alcohol, p-hydroxybenzyl alcohol, p-nitrobenzyl alcohol, 2- (p-fluorophenyl) ethanol, 2 -Aminophenethyl alcohol, 2-methoxybenzyl alcohol, 2-methyl-3-nitrobenzyl alcohol, 2-methylbenzyl alcohol, 2-nitrophenethyl alcohol, 2-phenylethanol, 3,4-dimethylbenzyl alcohol, 3-methyl- 2-Nitrobenzyl alcohol, 3-methyl-4-nitrobenzyl alcohol, 3-methylbenzyl alcohol, 4-fluorophenethyl alcohol, 4-hydroxy-3-methoxybenzyl alcohol, 4-methoxybenzyl alcohol, 4-methyl-3-3 Nitrobenzyl alcohol, 5-methyl-2-nitrobenzyl alcohol, DL-α-hydroxyethylbenzene, o- (trifluoromethyl) benzyl alcohol, p- (trifluoromethyl) benzyl alcohol, p-aminophenethyl Alcohols, alcohols such as p-hydroxyphenylethanol, p-methylbenzyl alcohol and S-phenethyl alcohol; phenols such as 4-methylphenol, 4-ethylphenol and 4-propylphenol and the like can be mentioned. Of these, those having a molecular weight of less than 500 are adsorbed on the abrasive particles by a hydrophobic group such as an alkyl group in the abrasive slurry, and therefore can be recovered together with the abrasive particles in the above regeneration step.

[Additive B: Additive having the ability to reduce the polishing rate]
As described above, the additive B is an additive for imparting storage stability and the like in the period from the preparation of the abrasive slurry to the use in the polishing step, and has the ability to reduce the polishing rate. Therefore, since the regenerated abrasive slurry is often used immediately, the additive B becomes an unnecessary component.
Examples of the compound corresponding to Additive B include preservatives, antibacterial agents, rust preventives and the like.

(Preservative)
Examples of preservatives include benzalkonium chloride, benzethonium chloride, 1,2-benzisothiazolin-3-one, (5-chloro) 2-methyl-4-isothiazolin-3-one, hydrogen peroxide, and hypochlorous acid. Acids and the like can be mentioned.

(Antibacterial agent)
Examples of the antibacterial agent include a quaternary ammonium salt type antibacterial agent, and examples thereof include tetramethylammonium chloride, tetraethylammonium chloride, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

(anti-rust)
Examples of the rust preventive include ethanolamine compounds such as N, N-diethylethanolamine, N, N-dimethylethanolamine, and aminoethylethanolamine.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Although the display of "%" is used in the examples, it represents "mass%" unless otherwise specified.

<< Preparation of Regenerated Abrasive Slurry 101 >>
(Preparation of unused abrasive slurry)
After adding the following abrasive particles and each additive to pure water, they were dispersed using a homogenizer to prepare 10 kg of an abrasive slurry having a CeO ₂ concentration (abrasive concentration) of 4000 mass ppm. This was used as an unused abrasive slurry. The CeO ₂ concentration was measured by ICP emission spectroscopy (inductively coupled plasma emission spectroscopy). Hereinafter, the CeO ₂ concentration was measured in the same manner.

Abrasive particles: Cerium oxide abrasive 40.0 g
Additive A: Ammonium polyacrylic acid salt (PAA, dispersant, molecular weight: 8000) 0.6 g
Additive A: 2-Ethylhexanol (cleaning agent, molecular weight: 130)
0.2g
Additive B: Hypochlorous acid (preservative, molecular weight: 52) 0.1 g

(Polishing process)
The surface to be polished was polished with a polishing cloth while supplying the prepared unused abrasive slurry to the surface to be polished using the polishing machine shown in FIG. Abrasive slurry was circulated and supplied at a flow rate of 5 L / min for polishing. A glass substrate of 65 mmΦ was used as the object to be polished, and a polishing cloth made of polyurethane was used. The polishing pressure on the polished surface was 9.8 kPa (100 g / cm ² ), the rotation speed of the polishing tester was set to 100 min ^-1 (rpm), and the polishing process was performed for 30 minutes. The thickness before and after polishing was measured with a Nikon Digimicro (MF501), the amount of polishing per minute (μm) was calculated from the thickness displacement, and the polishing rate (μm / min) was measured, which was set to 1.00. did. Pure water was used as the cleaning water for cleaning the polished portion.

(Abrasive slurry recovery process)
The abrasive slurry used in the polishing step was recovered together with the washing water, and this was used as a recovered abrasive slurry. The CeO ₂ concentration of the recovered abrasive slurry was 950 mass ppm, and the recovered amount was 20 kg.

(Regeneration process: Foreign matter removal process)
The recovered abrasive slurry was subjected to a foreign matter removal treatment using a hollow fiber filter having a pore size of 45 μm.

(Regeneration process: Dissolution treatment of the object to be polished)
The recovered abrasive slurry from which foreign matter had been removed by the foreign matter removing treatment was put into a tank equipped with a stirrer, and pure water was added as a solvent to the tank to adjust the CeO ₂ concentration to 12 mass ppm.

(Regeneration process: Additive removal process)
Next, 3166 L of pure water was removed by filtering the stirred recovered abrasive slurry for 16.63 hours using a filtration filter (ceramic filter manufactured by Noritake Co., Ltd., pore size 0.2 μm) at a flow rate of 200 L / h. , 0.27 kg of an additive-removed abrasive slurry having a CeO ₂ concentration of 107018 mass ppm was obtained. This was designated as a recycled abrasive slurry 101. The recovery rate of the abrasive particles was 75% before and after the additive removal treatment.

<< Preparation of recycled abrasive slurry 102 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 40 mass ppm in the object dissolution treatment, and the filtration time was set to 4.99 hours in the additive removal treatment. The reclaimed abrasive slurry 102 was prepared in the same manner except that 949 L was removed. The composition of the obtained regenerated abrasive slurry 102 is shown in Table 1.

<< Preparation of Recycled Abrasive Slurry 103 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 400 mass ppm in the object dissolution treatment, and the filtration time was 0.5 hours in the additive removal treatment. The reclaimed abrasive slurry 103 was prepared in the same manner except that 94 L was removed. The composition of the obtained regenerated abrasive slurry 103 is shown in Table 1.

<< Preparation of recycled abrasive slurry 104 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 12 mass ppm in the object dissolution treatment, and the filtration time was 16.63 hours in the additive removal treatment. The reclaimed abrasive slurry 104 was prepared in the same manner except that 3165 L was removed. The composition of the obtained regenerated abrasive slurry 104 is shown in Table 1.

<< Preparation of Regenerated Abrasive Slurry 105 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 40 mass ppm in the object dissolution treatment, and the filtration time was set to 4.99 hours in the additive removal treatment. The reclaimed abrasive slurry 105 was prepared in the same manner except that 949 L was removed. The composition of the obtained reclaimed abrasive slurry 105 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 106 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 400 mass ppm in the object dissolution treatment, and the filtration time was 0.49 hours in the additive removal treatment. The reclaimed abrasive slurry 106 was prepared in the same manner except that 94 L was removed. The composition of the obtained regenerated abrasive slurry 106 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 107 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 12 mass ppm in the object dissolution treatment, and the filtration time was 16.63 hours in the additive removal treatment. The regenerated abrasive slurry 107 was prepared in the same manner except that 3166 L was removed. The composition of the obtained reclaimed abrasive slurry 107 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 108 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 40 mass ppm in the object dissolution treatment, and the filtration time was set to 4.99 hours in the additive removal treatment. The reclaimed abrasive slurry 108 was prepared in the same manner except that 949 L was removed. The composition of the obtained regenerated abrasive slurry 108 is shown in Table 1.

<< Preparation of recycled abrasive slurry 109 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 400 mass ppm in the object dissolution treatment, and the filtration time was 0.5 hours in the additive removal treatment. The reclaimed abrasive slurry 109 was prepared in the same manner except that 94 L was removed. The composition of the obtained recycled abrasive slurry 109 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 110 >>
In the preparation of the reproduction abrasive slurry 101, pure water was added so that 12 ppm by weight CeO ₂ concentration in the object to be polished dissolution treatment, pure water filtration time as 16.59 hours additive removal treatment The reclaimed abrasive slurry 110 was prepared in the same manner except that 3157 L was removed. The composition of the obtained regenerated abrasive slurry 110 is shown in Table 1.

<< Preparation of recycled abrasive slurry 111 >>
In the preparation of the reproduction abrasive slurry 101, pure water was added so that the CeO ₂ concentration of 40 mass ppm at the object to be polished dissolution treatment, pure water filtration time as 4.95 hours additive removal treatment The reclaimed abrasive slurry 111 was prepared in the same manner except that 941 L was removed. The composition of the obtained reclaimed abrasive slurry 111 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 112 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 400 mass ppm in the object dissolution treatment, and the filtration time was 0.45 hours in the additive removal treatment. The reclaimed abrasive slurry 112 was prepared in the same manner except that 86 L was removed. The composition of the obtained regenerated abrasive slurry 112 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 113 >>
In the preparation of the reproduction abrasive slurry 101, pure water was added so that 12 ppm by weight CeO ₂ concentration in the object to be polished dissolution treatment, pure water filtration time as 16.63 hours additive removal treatment The reclaimed abrasive slurry 113 was prepared in the same manner except that 3166 L was removed. The composition of the obtained regenerated abrasive slurry 113 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 114 >>
In the preparation of the reproduction abrasive slurry 101, pure water was added so that the CeO ₂ concentration of 40 mass ppm at the object to be polished dissolution treatment, pure water filtration time as 4.99 hours additive removal treatment The reclaimed abrasive slurry 114 was prepared in the same manner except that 950 L was removed. The composition of the obtained regenerated abrasive slurry 114 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 115 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 400 mass ppm in the object dissolution treatment, and the filtration time was 0.5 hours in the additive removal treatment. The reclaimed abrasive slurry 115 was prepared in the same manner except that 95 L was removed. The composition of the obtained regenerated abrasive slurry 115 is shown in Table 1.

<< Preparation of reclaimed abrasive slurry 116 >>
In the preparation of the regenerated abrasive slurry 101, pure water was added so that the CeO ₂ concentration was 4 mass ppm in the object dissolution treatment, and the filtration time was 49.9 hours in the additive removal treatment. The reclaimed abrasive slurry 116 was prepared in the same manner except that 9499 L was removed. The composition of the obtained regenerated abrasive slurry 116 is shown in Table 1.

<< Evaluation of Recycled Abrasive Slurry 101-116 >>
The following evaluations were carried out for each of the regenerated abrasive slurries prepared above. The evaluation results are shown in Table 2.

(1) Quantification of components contained in the abrasive slurry before and after the additive removal treatment Pure water, CeO ₂ , PAA in the recovered abrasive slurry before the additive removal treatment and the regenerated abrasive slurry obtained after the additive removal treatment. , 2-Ethylhexanol, hypochlorous acid and SiO ₂ (abrasive) were quantified using high performance liquid chromatography (HPLC) manufactured by Shimadzu Corporation. In addition, the recovery rate of the abrasive particles (CeO ₂ ) was calculated before and after the additive removal treatment.

(2) Evaluation of Polishing Rate Using each of the prepared regenerated abrasive slurry, the same operation as in the polishing step using the unused abrasive slurry was carried out, and the polishing rate (μm / min) was measured. From the obtained polishing rate, a relative value when the polishing rate was 1.00 when the polishing step was performed using the unused abrasive slurry was obtained and evaluated according to the following criteria.

◯: 0.9 or more Δ: 0.5 or more and less than 0.9 ×: less than 0.5

(3) Measurement of the number of defects After performing the same operation as the polishing process using the above-mentioned unused abrasive slurry using each of the prepared recycled abrasive slurry, the surface of the object to be polished is exposed under the light source of a mercury lamp. It was observed in detail with an inspection device (Olympus AL2000, Olympus Corporation), and the number of irregularities having a length of 0.2 to 1.0 μm was measured and used as the number of defects. The number of defects per unit area was calculated from the area of the surface of the object to be polished in the range where the number of defects was measured. The values are shown in Table 2.

As is clear from Tables 1 and 2, the abrasive concentration is maintained within the range of 0.2 to 3000% with respect to the abrasive concentration of the unused abrasive slurry when used for polishing the object to be polished. The regenerated abrasive slurry of the present invention obtained by performing a regeneration step of recovering the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles is compared with the abrasive slurry of the comparative example. As a result, the recovery rate of abrasive particles (CeO ₂ ) is high, the polishing speed is excellent, and the number of defects is reduced. Therefore, according to the method for regenerating the abrasive slurry of the present invention, it can be said that the abrasive slurry having a high polishing rate can be efficiently regenerated.
Further, in the recycled abrasive slurry 113 to 115 of the comparative example, the abrasive concentration during the regeneration process exceeded 3000% with respect to the abrasive concentration of the unused abrasive slurry, so that the recovered abrasive slurry was lost. , And the recovery rate of the abrasive particles is low. Further, in the reclaimed abrasive slurry 116 of the comparative example, the amount of the additive A recovered was less than 0.2% during the reclaiming process with respect to the abrasive concentration of the unused abrasive slurry. Is reduced, and the polishing speed is low.

As described above, the present invention is suitable for providing a method for regenerating an abrasive slurry capable of efficiently regenerating an abrasive slurry having a high polishing rate.

1 Abrasive 2 Polishing platen 3 Abrasive 4 Abrasive slurry 5 Slurry nozzle 6 Flow path 7 Washing water 8 Washing water injection nozzle 9 Flow path 10 Cleaning liquid 20 Filter Filtration device 21 Tank 22 Recovered abrasive slurry 23 Circulation piping 24 Three-way valve 25 Stirrer 26 Filtration filter 27 On-off valve D1, D2 Pump F Abrasive cloth M Motor H Holder T ₁ Slurry tank T ₂ Wash water storage tank T ₃ Wash liquid storage tank

Claims (2)

An abrasive slurry that regenerates the recovered abrasive slurry after polishing an object to be polished containing silicon oxide as a main component using an abrasive slurry containing abrasive particles and a plurality of types of additives. It ’s a playback method,
The relative abrasive concentration of unused abrasive slurry when used in polishing of the object to be polished (wt%), maintaining the abrasive concentration (mass%) in the range from 0.2 to 1 000% of However, among the additives contained in the recovered abrasive slurry, the additive having a molecular weight of 500 or more and the additive adsorbed on the abrasive particles are recovered together with the abrasive particles. A method for regenerating an abrasive slurry, which is characterized by the above. While maintaining the abrasive concentration (mass%) within the range of 1 to 1000% with respect to the abrasive concentration (mass%) of the unused abrasive slurry when used for polishing the object to be polished, the above. The method for regenerating an abrasive slurry according to claim 1, wherein a regeneration step is performed.

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